Method and device for cnt length control

ABSTRACT

A method for manufacturing a carbon nanotube (CNT) of a predetermined length is disclosed. The method includes generating an electric field to align one or more CNTs and severing the one or more aligned CNTs at a predetermined location. The severing each of the aligned CNTs may include etching the predetermined location of the one or more aligned CNTs and applying a voltage across the one or more etched CNTs.

BACKGROUND

Carbon nanotubes (CNTs) are carbon allotropes consisting of carbon foundin abundance all over the world. CNTs are formed in such a manner thatone carbon element is bonded to other carbon elements while making ahexagonal honeycomb-pattern in a tube-shape. The diameter of a CNT is inthe order of a few nanometers. Recently, CNTs have been proposed as abasic element for the next generation of nanoelectronic, mechanical andnanomedical systems due to their nanoscale dimensions and outstandingmaterials properties, such as ballistic electronic conduction, immunityfrom electromigration effects at high current densities, and transparentconduction. However as commonly synthesized, CNTs vary in their diameterand chiral angle, and these physical variations may result in changes intheir electronic and/or optical behavior.

SUMMARY

In one aspect, a method for manufacturing a carbon nanotube (CNT) of apredetermined length includes generating an electric field to align oneor more CNTs and severing the one or more aligned CNTs at apredetermined location. The aligned CNTs may be severed by etching thepredetermined location of the one or more aligned CNTs and applying avoltage across the one or more etched CNTs.

In another aspect, a device for manufacturing a carbon nanotube (CNT) ofa predetermined length, includes at least one pair of source and drainelectrodes to align the CNTs between the source and drain electrodes,and an electronic device to generate an electric field between thesource and drain electrodes to align the one or more CNTs locatedbetween the source and drain electrodes, and to apply a voltage to severthe one or more CNTs at a predetermined location.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of an illustrative embodiment of a devicefor manufacturing carbon nanotubes (CNTs) of a predetermined length.

FIGS. 2( a) and 2(b) illustrate schematic diagrams of anotherillustrative embodiment of a device for manufacturing CNTs of apredetermined length.

FIG. 3 is a schematic diagram illustrating a top view of the portion “A”of the device shown in FIG. 1.

FIGS. 4( a) and 4(b) illustrate top views of the portion “A” of thedevice of FIG. 1 for illustrating an aligning and etching process inaccordance with one example.

FIGS. 5( a) and 5(b) illustrate schematic diagrams showing across-section of the device shown in FIG. 1 for illustrating an etchingprocess.

FIG. 6 is a top view of the portion “A” of the device of FIG. 1 forillustrating a severing process in accordance with one example.

FIG. 7 is a schematic diagram of illustrative severed segments of CNTswith the same or substantially similar diameters.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented herein. It will be readily understood that the aspects of thepresent disclosure, as generally described herein, and illustrated inthe Figures, can be arranged, substituted, combined, separated, anddesigned in a wide variety of different configurations, all of which areexplicitly contemplated herein.

Device for Manufacturing a Carbon Nanotube (CNT) of a PredeterminedLength

In one aspect, a device for manufacturing a carbon nanotube (CNT) of apredetermined length is provided. As used herein, the “carbon nanotubes(CNTs)” refer to allotropes of carbon with a cylindrical nanostructure.The CNTs may be single-walled or multi-walled. Single-walled CNTs referto CNTs in which one-atom-thick layer of graphite is wrapped into acylinder, and multi-walled CNTs refer to CNTs in which multiple sheetsof graphite are arranged in concentric cylinders. The predeterminedlength of CNTs may refer to a desired length of CNTs depending on theiruse and/or application. For example, CNTs of relatively longer lengthmay be used for a flat display, such as a field emission display (FED),and CNTs of shorter length may be used for a super capacitor. Thepredetermined length of each CNT can be in the range of approximately1-500 μm, approximately 10-400 μm, or approximately 100-250 μm.

In the present disclosure, the CNTs can be fabricated using, withoutlimitation, a chemical vapor deposition (CVD), arc discharge, or laserablation, which are well-known in the art. By way of example, CNTs aregrown using chemical vapor deposition (CVD) by placing iron catalysts inlithographically patterned stripes approximately 50-100 μm apart on asubstrate. The CNTs can be grown from the catalyst stripes to thecatalyst stripes such that the CNTs are formed between the catalyststripes. For additional detail on growing CNTs using CVD, see Seong JunKang, et al., “High-performance electronics using dense, perfectlyaligned arrays of single-walled carbon nanotubes”, naturenanotechnology, 25 Mar. 2007, 230-236, Vol. 2, 2007 Nature PublishingGroup, which is incorporated by reference herein in its entirety.

FIG. 1 is a schematic diagram of an illustrative embodiment of a device100 for manufacturing CNTs of a predetermined length. FIG. 1 shows thedevice 100 including at least one pair of source and drain electrodes111 and 112 on a substrate 110. The source electrode 111 is representedby slashed lines to distinguish the source electrode 111 from the drainelectrode 112 clearly. The substrate 110 is configured to support one ormore CNTs. In some embodiments, the substrate 110 may be a quartz wafer,silicon (S), silicon carbide (SiC), silicon germanium (SiGe), galliumarsenide (GaAs), or a sapphire wafer on which the CNTs are aligned. Thesubstrate 110 is not limited to the illustrated embodiment of FIG. 1,but can have any configuration, such as flat rectangular or square type,as long as it can support one or more CNTs.

As depicted in FIG. 1, the device 100 includes at least one pair of thesource and drain electrodes 111 and 112, and an electronic device 120operably (for example, electrically) connected to the source and drainelectrodes 111 and 112. The electronic device 120 is configured togenerate an electric field between the source and drain electrodes 111and 112 to align one or more CNTs located between the source and drainelectrodes 111 and 112. For example, the electronic device 120 may applya voltage to the drain electrode 112, and the electric filed may begenerated across the CNTs due to the voltage difference between thesource and drain electrodes 111 and 112. As used herein, the term,“electric field” refers to an electrical energy with energy densityproportional to the square of the field intensity, which may exert aforce on other electrically charged objects. The CNTs can be arrangedalong with the direction of the generated electric field, which will bedescribed in detail later. As examples of the electronic device 120, avoltage source, such as a LED voltage source or a Zener voltage sourcecan be used. The electronic device 120 can control an amount of thevoltages provided to the drain electrode 112 to align the CNTs. In someembodiments, the electronic device 120 can be controlled to apply to thedrain electrode 112 approximately AC 1-100V, or approximately AC 10-50V.

The electronic device 120 is further configured to apply a voltage tosever the one or more CNTs at a predetermined location. As used herein,the term “severed” or “sever” refers to a physical separation (forexample, split or cut) of CNTs. The “predetermined location” refers to adesired location of CNTs to be severed. The predetermined location ofCNTs will be described in detail in conjunction with FIG. 4. The sourceand drain electrodes 111 and 112 can be arranged to align the CNTstherebetween and can be composed of any conductive material, such aswell known semiconductor material having conductivity, or a metal.

The source electrode 111 and the drain electrode 112 can be located onthe substrate 110 to make at least one alignment area 113. As usedherein, the term “alignment area” refers to an area to align the one ormore CNTs. The term “alignment area” further refers to an area toreceive the one or more CNTs. The term “alignment area” still furtherrefers to an area formed between the source electrode 111 and the drainelectrode 112. The term “alignment area” still further refers to an areato receive an electric field generated between the source and drainelectrodes 111 and 112 in response to a voltage of the electronic device120. The function and size of the alignment 113 will be described indetail hereinafter.

In an illustrative embodiment, the source electrode 111 can beconfigured to have a main portion 111 a and one or more branchedportions 111 b extended from the main portion 111 a. The drain electrode112 can be configured to have a main portion 112 a and one or morebranched portions 112 b extended from the main portion 112 a. The sourceand drain electrodes 111 and 112 can be located on the substrate 110such that the alignment area 113 can be formed between the branchedportions 111 b and 112 b of the source and drain electrodes 111 and 112.

Herein, the main portions 111 a and 112 a of the source and drainelectrodes 111 and 112 refer to an extending portion in one direction(for example, in a longitudinal direction), respectively. The branchedportions 111 b and 112 b of the source and drain electrodes 111 and 112refer to portions branched out from the main portions 111 a and 112 a inperpendicular to the main portions 111 a and 112 a, respectively. Asdepicted in FIG. 1, the branched portions 111 b and 112 b may behorizontally branched from the main portions 111 a and 112 a,respectively. Although FIG. 1 illustrates three (3) branched portions111 b of the source electrode 111 and three (3) branched portions 112 bof the drain electrode 112, it will be apparent to one of skill in theart that more than three (3) branched portions can be branched out fromthe main portions 111 a and 112 a, respectively.

FIG. 1 further illustrates that the branched portions 111 b of thesource electrode 111 and the branched portions 112 b of the drainelectrode 112 may be alternately arranged on the substrate 110, with apredetermined distance “d1” to provide the alignment area 113 betweenthe source and drain electrodes 111 and 112. The predetermined distance“d1” and the alignment area 113 will be described in detail withreference to FIG. 3 hereinafter.

Although FIG. 1 illustrates the source and drain electrodes 111 and 112which form a maze-like pattern in which the branched portions 111 b and112 b of the source electrode 111 and the drain electrode 112 arealternately arranged on the substrate 110, it will be apparent to thoseof skilled in the art that the source and drain electrodes 111 and 112can have various configurations to provide the alignment area 113 on thesubstrate 110.

As one embodiment, FIG. 2( a) illustrates that a source electrode 211and a drain electrode 212 each having a zigzag-type structure arearranged on the substrate 110 with the predetermined distance “d1” toprovide the alignment area 113. Each of the source electrode 211 and thedrain electrode 212 forms the zigzag-type structure by having multiplenumbers of corners with a predetermined angle “α.” By way of example,the predetermined angle α can be about 90 degrees (°) to 180 degrees (°)or about 120 degrees (°) to 150 degrees (°).

As another embodiment, FIG. 2( b) illustrates that a source electrode221 and a drain electrode 222 having a bar-type structure are arrangedin parallel on the substrate 110 with the predetermined distance “d1” toprovide the alignment area 113. Although the maze-like pattern, thezigzag pattern and the parallel bar pattern are illustrated, it will beapparent to one of skill in the art that various patterns of the sourceand drain electrodes can be configured to provide the alignment area 113within the scope of the present disclosure.

FIG. 3 is a schematic diagram illustrating a top view of the portion “A”of the device shown in FIG. 1. FIG. 3 illustrates the alignment area 113defined by the main portions 111 a and 112 a, and the branched portions111 b and 112 b of the source and drain electrodes 111 and 112.Particularly, a width of the alignment area 113 can be determined by apredetermined distance “d1” between the branched portions 111 b and 112b of the source and drain electrodes 111 and 112. As used herein, thepredetermined distance “d1” also refers to a length equal to or greaterthan a length of CNTs to be aligned on the alignment area 113, whichwill be described in detail hereinafter. A length of the alignment area113 can be determined by a distance “d2” between the main portions 111 aand 112 a of the source and drain electrodes 111 and 112. For example,the predetermined distance “d1” between the branched portions 111 b and112 b can be about 2-1000 μm, about 20-800 μm, or about 200-500 μm. Thedistance “d2” between the main portions 111 a and 112 a can be about10-5000 μm, about 100-4000 μm, or about 1000-2500 μm. Accordingly, thesize of the alignment 113 can be controlled by the predetermineddistance “d1” and the distance “d2.” By way of example, if thepredetermined distance “d1” between the branched portions 111 b and 112b is longer, the width of the alignment area 113 is wider so that longerCNTs can be aligned on the alignment area 113. Further, if the distance“d2” between the main portions 111 a and 112 a is longer, the length ofthe alignment area 113 is longer so that a large number of the CNTs canbe aligned on the alignment area 113.

In some embodiments, the predetermined distance “d1” between thebranched portion 111 b and the branched portion 112 b may be determinedbased on a desired length of the one or more CNTs which are aligned inthe alignment area 113. Because the one or more CNTs aligned in thealignment area 113 are severed into two segments through a severingprocess which will be described hereinafter, the predetermined distance“d1” can be determined considering the desired length of the CNTs.Assuming that the desired length of a CNT is 10 μm and the CNT issevered into two segments, the predetermined distance “d1” is about 20μm. However, the predetermined distance “d1” can be a little longer than20 μm to consider the loss of length of the CNT during the severingprocess.

The device 100 can further include an etching device (not shown) to etchthe predetermined locations of the aligned CNTs. The etching device ofdevice 100 may include any etching device suitable to etch CNTs, suchas, a plasma etching device or reactive ion etching (RIE) device. By wayof an example, the plasma etching device may include a plasma chamber, agas input, gas evacuation holes, a top electrode connected toradio-frequency (RF) source, a bottom electrode connected to a ground. Aplasma etching can be performed by ionizing a gas mix, for example,oxygen-containing gas, inside the plasma chamber to obtain ions. Theionization of the gases is done by RF excitation emitted by the topelectrode and resulting ions react with the target material, forexample, a CNT layer with a masked portion, which is placed on thebottom electrode.

In addition, the device 100 can further include a separator to separateCNTs in accordance with a diameter of the CNTs. The separator caninclude a centrifugation device, such as an ultracentrifugation device,a low speed centrifugation device, or a high speed centrifugationdevice. The centrifugation device may sort the CNTs based on thedifference in buoyant densities of the CNTs, the diameters in densitygradients, or electronic types of the CNTs. Additional details on theseparation will be described in connection with FIG. 7.

Method for Manufacturing a Carbon Nanotube (CNT) of a PredeterminedLength

FIG. 4( a) illustrates a top view of the boxed portion “A” shown in FIG.1 for illustrating an alignment of one or more CNTs. In one embodiment,a CNT solution containing one or more CNTs 115 can be provided in thealignment area 113 of the substrate 110 by adding to the alignment area113 the CNT solution, pouring to the alignment area 113 the solution,immersing the substrate 110 having the alignment area 113 in the CNTsolution, soaking the substrate 110 having the alignment area 113 in theCNT solution, supplying to the alignment area 113 the CNT solution, orinjecting the CNT solution into the alignment area 113 of the substrate110 using any type of liquid injector. Herein, the one or more CNTs 115can be fabricated using well known techniques, such as a CVD, arcdischarge or large ablation, as described above. In some embodiments,when the one or more CNTs 115 are grown using CVD technique, the CNTs115 can have the substantially same length by patterning the CNTs 115 tohave the same length using a photolithographic method. As used herein,the CNT solution is formed by dispersing the CNTs 115 into water orother solvents, such as hydrocarbons, halogenated hydrocarbons, ethers,nitrogen compounds and sulfur compounds, without limitation. The CNTs115 may have diameters of about 1-20 nm, 5-15 nm, or 8-10 nm, andlengths of about 2-1000 μm, about 20-800 μm, or about 200-500 μm.

In some embodiments, a size (for example, a width) of the alignment area113 may be determined by the predetermined distance “d1,” as describedabove. The predetermined distance “d1” may be substantially equal to orlarger than the length of the CNTs 115. Thus, if the CNT solution may bepoured on the alignment area 113 of the substrate 110, the CNTs 115contained in the CNT solution can be provided in the alignment area 113.Here, the CNTs 115 may be dispersed in the alignment area 113. Thedispersed CNTs may be aligned in the alignment area 113 in response toan electric field. Particularly, the electronic device 120 (shown inFIG. 1) may apply to the source and drain electrodes 111 and 112 avoltage to generate an electric field between the branched portion 111 bof the source electrode 111 and the branched portion 112 b of the drainelectrode 112. FIG. 4( a) illustrates that in response to the electricfield, the CNTs 115 dispersed in the alignment area 113 can be alignedin parallel to the electric field in the alignment area 113 due toelectrostatic forces acting on the CNTs 115.

The CNTs 115 aligned in the alignment area 113 can be severed into twosegments at predetermined locations. In some embodiments, the CNTs 115can be severed by etching the predetermined locations of the alignedCNTs, and applying a voltage across the CNTs to cut the etchedpredetermined locations of the CNTs. Accordingly, The CNTs can besevered into two segments through the etching and the cutting of theCNTs at the predetermined locations of the CNTs. The severing processwill be described in detail hereinafter.

FIG. 4( b) illustrates the aligned CNTs 115 with predetermined locations116 that is subject to an etching process. The predetermined locations116 can be determined to obtain a desired length of severed segments ofthe CNTs 115. For example, if each of the CNTs 115 is severed into twosegments and each segment has the same desired length, the predeterminedlocation 116 can be located at a middle of a total length of each of theCNTs 115.

FIG. 5( a) and FIG. 5( b) are schematic diagrams showing an illustrativeembodiment of a cross-section of the device shown in FIG. 1 forillustrating the etching process. The predetermined locations 116 of theCNTs 115 are subject to an etching process by the etching device (notshown), such as a plasma etching device or a reactive ion etching (RIE)device. In order to etch the predetermined locations 116 of the CNTs115, a mask layer 130 can be formed on the CNTs 115 aligned in thealignment area 113, as shown in FIG. 5( a). FIG. 5( a) shows, thesubstrate 110 on which at least one alignment area 113 is formed betweenthe branched portion 111 b of the source electrode and the branchedportion 112 b of the drain electrode, and one or more CNTs 115 alignedin the alignment area 113. The mask layer 130 having a slit 131 may bedeposited to cover the CNTs 115. The slit 131 (i.e. an unmasked portionof mask layer 130) has a width “a” which is substantially the same asthat of the predetermined location 116 of the CNTs 115. FIG. 5( a)further shows that the mask layer 130 is deposited on the substrate 110such that the slit 131 is placed on the predetermined location 116 ofthe CNTs 115.

In some embodiments, the portions of the CNTs 115 exposed through theslit 131 of the mask layer 130 are available for etching, for example,directional etching. As used herein, the term “directional etching”refers to directional removal of a material from a substrate via aphysical or a chemical process using an etchant substance. The etchantsubstance may be a corrosive liquid or a chemically active ionized gas(for example, a plasma). The directional etching can include, withoutlimitation, an oxygen plasma etching or a reactive ion etching (RIE).For example, the oxygen plasma etching can be performed by ionizing agas mix, for example, oxygen-containing gas, inside the plasma chamberto obtain ions. The ionization of the gases is done by RF excitationemitted by the top electrode and resulting ions react with a targetmaterial, for example, a CNT layer with a masked portion, which isplaced on the bottom electrode. In addition, the reactive ion etching(RIE) is an etching technology which uses a chemically reactive plasmato remove a desired portion of a material (for example, CNTs). Theplasma is generated under low pressure (vacuum) by an electromagneticfield. High-energy ions from the plasma react with the material suchthat the desired portion of the material is removed.

As a result of the directional etching performed on the predeterminedlocations 116 of the CNTs 115, only the unmasked portions having thewidth of “a” are etched directionally, and thus etched portions 117having width of “a” are formed in the middle of the lengths of the CNTs115 as illustrated in FIG. 5( b).

FIG. 6 shows the severing of the etched portions 117 of the CNTs 115.FIG. 6 is a top view of the boxed portion “A” of FIG. 1 for illustratingthe severing process in accordance with one example. The etched portions117 (shown in FIG. 5( b)) of the CNTs 115 can be cut in response to theelectric field generated between the source electrode 111 and the drainelectrode 112 (for example, the branched portion 111 b of the sourceelectrode 111 and the branched portion 112 b of the drain electrode 112as depicted in FIG. 1). The electric field can be generated by applyinga voltage through the electronic device 120 (shown in FIG. 1). In someembodiments, a voltage is applied from the electronic device 120 to thedrain electrode 112, and thus a current is introduced through the CNTs115. For example, the voltage may be ranged in about 2-2.5 V, about 1-5V, or about 0.5-10 V, and the current may be ranged in about 10-15 μA,about 5-30 μA, or about 2.5-60 μA. The range of the applied voltage tosever the etched portions 117 of the CNTs 115 can be experimentallyobtained based on diameters of the CNTs 115. The range of the introducedcurrent may vary with the applied voltage. In response to the introducedcurrent, the etched portions 117 of the CNTs 115 are weaken, and theCNTs 115 are ultimately severed into two segments with respect to theetched portions 117.

Each of the severed segments of the CNTs 115 may have a length in therange of approximately 1-500 μm, 10-400 μm, or 100-250 μm. The severedsegments of the CNTs 115 may have substantially the same length ordifferent length depending on the predetermined locations of the CNTs115. In some embodiments, when each of the CNTs 115 has onepredetermined location 116 and the predetermined location 116 is locatedon the middle of the total length of each of the CNTs 115, the severedsegments of the CNTs 115 have substantially the same length. In anotherembodiment where the predetermined location 116 is placed on one thirdof the total length of each of the CNTs 115, each of the CNTs 115 mayhave one segment having one third of the total length of each CNT andthe other segment having two third of the total length of each CNT.

FIG. 7 is a schematic diagram illustrating groups of severed segments118 of the CNTs 115 of FIG. 6 with the same or substantially similardiameters. The severed segments 118 of the CNTs 115 may be detached fromthe substrate 110 (shown in FIG. 1), and the detached segments 118 ofthe CNTs having various diameters may be sorted a centrifugation. As anexample of the centrifugation, an ultracentrifugation using densitydifferentiation can be used. For example, in response to a centripetalforce, the severed segments 118 having different diameters can beseparated in different layers of a centrifuge tube according to thedifference in buoyant densities. Herein, the buoyant densities may referto mass per volume of the CNTs. The group of the severed segments 118with smaller diameters can be placed in a higher layer in the centrifugetube and the group of the severed segments 118 with larger diameters canbe placed in a lower layer in the centrifuge tube. Thus, the layer bylayer removal from the centrifuge tube can be performed to extract eachlayer. For example, by removing a highest layer from the centrifugetube, the severed segments 118 of the CNTs 115 with smallest diameterscan be extracted. Additional details on the sorting method using thedifference in buoyant densities, see “Sorting carbon nanotubes byelectronic structure using density differentiation,” by Michael S.Arnold et al., Nature nanotechnology, vol 1, published on October 2006,which is incorporated by reference herein in its entirety.

In other sorting methods, the CNTs 115 can be classified according totheir diameters in density gradients, or electronic types. Additionaldetails on the sorting method using diameters in density gradients, andelectronic types, see “Enrichment of single-walled carbon nanotubes bydiameter in density gradients,” by Arnold, M. S. et al., Nano Lett. 5,713-718 (2005); and “Bulk separative enrichment in metallic orsemiconducting single-walled carbon nanotubes,” by Chen, Z. H. et al.,Nano Lett. 3, 1245-1249 (2003), which are incorporated by referenceherein in their entireties.

In another embodiment, the sorting of the CNTs 115 according to theirdiameters can be performed prior to the severing process. For example,the CNTs 115 having various diameters can be sorted according to theirdiameters by the aforementioned sorting method, and then the CNTs 115with the same or similar diameters can undergo the severing process asillustrated with respect to FIGS. 4 to 6.

As illustrated above, one or more CNTs can be severed into two segmentswith a desired length by etching a predetermined location of the CNTsand applying an electric field to the etched portion of the CNTs.Further, the predetermined location of the CNTs can be controlled toadjust the length of the segments of the CNTs or the number of thesegments of the CNTs. Accordingly, the CNTs with the desired length canbe manufactured with a simple and cost-effective method.

One skilled in the art will appreciate that, for this and otherprocesses and methods disclosed herein, the functions performed in theprocesses and methods may be implemented in differing order.Furthermore, the outlined steps and operations are only provided asexamples, and some of the steps and operations may be optional, combinedinto fewer steps and operations, or expanded into additional steps andoperations without detracting from the essence of the disclosedembodiments.

The present disclosure is not to be limited in terms of the particularembodiments described in this application, which are intended asillustrations of various aspects. Many modifications and variations canbe made without departing from its spirit and scope, as will be apparentto those skilled in the art. Functionally equivalent methods andapparatuses within the scope of the disclosure, in addition to thoseenumerated herein, will be apparent to those skilled in the art from theforegoing descriptions. Such modifications and variations are intendedto fall within the scope of the appended claims. The present disclosureis to be limited only by the terms of the appended claims, along withthe full scope of equivalents to which such claims are entitled. It isto be understood that this disclosure is not limited to particularmethods, reagents, compounds compositions or biological systems, whichcan, of course, vary. It is also to be understood that the terminologyused herein is for the purpose of describing particular embodimentsonly, and is not intended to be limiting.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to embodiments containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should be interpreted to mean “at least one”or “one or more”); the same holds true for the use of definite articlesused to introduce claim recitations. In addition, even if a specificnumber of an introduced claim recitation is explicitly recited, thoseskilled in the art will recognize that such recitation should beinterpreted to mean at least the recited number (e.g., the barerecitation of “two recitations,” without other modifiers, means at leasttwo recitations, or two or more recitations). Furthermore, in thoseinstances where a convention analogous to “at least one of A, B, and C,etc.” is used, in general such a construction is intended in the senseone having skill in the art would understand the convention (e.g., “asystem having at least one of A, B, and C” would include but not belimited to systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, and/or A, B, and Ctogether, etc.). In those instances where a convention analogous to “atleast one of A, B, or C, etc.” is used, in general such a constructionis intended in the sense one having skill in the art would understandthe convention (e.g., “a system having at least one of A, B, or C” wouldinclude but not be limited to systems that have A alone, B alone, Calone, A and B together, A and C together, B and C together, and/or A,B, and C together, etc.). It will be further understood by those withinthe art that virtually any disjunctive word and/or phrase presenting twoor more alternative terms, whether in the description, claims, ordrawings, should be understood to contemplate the possibilities ofincluding one of the terms, either of the terms, or both terms. Forexample, the phrase “A or B” will be understood to include thepossibilities of “A” or “B” or “A and B.”

In addition, where features or aspects of the disclosure are describedin terms of Markush groups, those skilled in the art will recognize thatthe disclosure is also thereby described in terms of any individualmember or subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, such as in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as “up to,” “at least,” and the like include the number recited andrefer to ranges which can be subsequently broken down into subranges asdiscussed above. Finally, as will be understood by one skilled in theart, a range includes each individual member. Thus, for example, a grouphaving 1-3 cells refers to groups having 1, 2, or 3 cells. Similarly, agroup having 1-5 cells refers to groups having 1, 2, 3, 4, or 5 cells,and so forth.

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

1. A method for manufacturing a carbon nanotube (CNT) of a predeterminedlength, comprising: generating an electric field to align one or moreCNTs; and severing the one or more aligned CNTs at a predeterminedlocation.
 2. The method of claim 1, wherein severing the one or morealigned CNTs comprises: etching the predetermined location of the one ormore aligned CNTs; and applying a voltage across the one or more etchedCNTs.
 3. The method of claim 1, further forming one or more aligned CNTsusing a chemical vapor deposition (CVD).
 4. The method of claim 1,wherein generating the electric field comprises: providing a solutioncontaining the one or more CNTs on a substrate; and applying a voltageto generate the electric field to align the CNTs on the substrate. 5.The method of claim 1, wherein generating the electric field comprises:locating the one or more CNTs between two electrodes; and applying avoltage to generate the electric field between the two electrodes toalign the CNTs perpendicular to the two electrodes.
 6. The method ofclaim 1, further comprising: depositing on the aligned CNTs a mask layerhaving a slit to etch the predetermined location of the CNTs.
 7. Themethod of claim 6, wherein etching is performed by a directionaletching.
 8. The method of claim 7, wherein the directional etchingcomprises an oxygen plasma etching or a reactive ion etching (RIE). 9.The method of claim 1, further comprising separating the severed CNTs inaccordance with a diameter of each of the CNTs.
 10. The method of claim9, wherein the separation is performed by a centrifugation.
 11. Themethod of claim 1, wherein the predetermined location is located at amiddle of a total length of each of the CNTs.
 12. The method of claim11, wherein lengths of the severed CNTs are substantially the same. 13.The method of claim 1, wherein the predetermined length of each of theCNTs is in the range of approximately 1-500 μm.
 14. A device formanufacturing a carbon nanotube (CNT) of a predetermined length,comprising: at least one pair of source and drain electrodes configuredto align the CNTs between the source and drain electrodes; and anelectronic device configured to generate an electric field between thesource and drain electrodes to align the one or more CNTs locatedbetween the source and drain electrodes, and to apply a voltage to severthe one or more CNTs at a predetermined location.
 15. The device ofclaim 14, further comprising an etching device to etch a predeterminedlocation of the aligned CNTs by using a directional etching
 16. Thedevice of claim 15, wherein the directional etching comprises an oxygenplasma etching or a reactive ion etching (RIE).
 17. The device of claim15, wherein the electronic device applies the voltage across the etchedCNTs in order to sever the CNTs at the predetermined location of each ofthe CNTs.
 18. The device of claim 15, wherein the predetermined locationis located at a middle of a total length of each of the CNTs.
 19. Thedevice of claim 16, further comprising a separator to separate thesevered CNTs in accordance with a diameter of the CNTs.
 20. The deviceof claim 14, wherein each of the source and drain electrodes comprise amain portion and one or more branched portions perpendicular from themain portion, such that the branched portions of the source electrodeand drain electrode are alternately arranged and are uniformly spacedapart.